New Method for the Fluorimetric Determination of Guanidino Compounds with Benzoin

Abstract

A new fluorimetric method for the precise and rapid determination of guanidino compounds with benzoin is described. This is based on their reaction in an aqueous potassium hydroxide solution with benzoin (dissolved in methylcellosolve), in the presence of β-mercaptoethanol and sodium sulfite, while the pH of the reaction mixture is maintained at 9.2 after the reaction. This method requires heating at 100° for only 10 min. The excitation and emission maximum wavelengths of the fluorescence from these compounds are at around 325 and 435 nm, respectively. The method is simple, selective for guanidine and monosubstituted guanidino compounds (including peptides with one or two arginyl residues) and sensitive ; almost all the compounds can be determined at concentrations as low as 40-170 pmol/ml.